Compaction Characteristics of Municipal Solid Waste

Compaction characteristics of municipal solid waste (MSW) were determined in the laboratory and in the field as a function of moisture content, compactive effort, and seasonal effects. Laboratory tests were conducted on manufactured wastes using modified and 4X modified efforts. Field tests were conducted at a MSW landfill in Michigan on incoming wastes without modifications to size, shape, or composition, using typical operational compaction equipment and procedures. Field tests generally included higher efforts and resulted in higher unit weights at higher water contents than the laboratory tests. Moisture addition to wastes in the field was more effective in winter than in summer due to dry initial conditions and potential thawing and softening of wastes. The measured parameters in the laboratory were ${\gamma }_{d\text{max-mod}}=5.2\text{kN}/{\text{m}}^3$ , $w_{\text{opt-mod}}=65\mathrm{\%}$ , ${\gamma }_{d\text{max-}4\times \text{mod}}=6.0\text{kN}/{\text{m}}^3$ , and $w_{\text{opt-}4\times \text{mod}}=56\mathrm{\%}$ ; in the field with effort were ${\gamma }_{d\text{max-low}}=5.7\text{kN}/{\text{m}}^3$ , $w_{\text{opt-low}}=70\mathrm{\%}$ ; ${\gamma }_{d\text{max-high}}=8.2\text{kN}/{\text{m}}^3$ , and $w_{\text{opt-high}}=73\mathrm{\%}$ ; and in the field with season were ${\gamma }_{d\text{max-cold}}=8.2\text{kN}/{\text{m}}^3$ , $w_{\text{cold}}=79.5\mathrm{\%}$ , ${\gamma }_{d\text{max-warm}}=6.1\text{kN}/{\text{m}}^3$ , and $w_{\text{warm}}=70.5\mathrm{\%}$ . Soil compaction theory was reasonably applicable to wastes with the exception that the $G_s$ of waste solids increased with compactive effort resulting in steep degree of saturation curves and low change in $w_{\text{opt}}$ between efforts. Moisture addition to wastes during compaction increased the workability, the unit weight, and the amount of incoming wastes disposed, and reduced the compaction time. The combined effects have significant environmental and economic implications for landfill operations.